<p>This paper investigates the relationship between agency cost, ownership structure and corporate governance mechanisms. Though previous studies of agency problems, corporate governance mechanisms or ownership variables suffer from endogeneity, with respect to the corporate governance it is unclear as to which variables are endogenous and which are exogenous. This study, using the Durbin-Wu-Hausman test for endogeneity, confirms noendogeneity issues should be addressed. Furthermore, addressing the issue of non-linearity, this study confirms that the relationship between agency costs, ownership structures and corporate governance mechanisms are non-linear. Using a balanced panel of 79 New Zealand-listed firms, this study employs a non-linear panel data method using Tobit. Apart from block-holders’ ownership, leverage, dividend, non-executive directors and audit committees, managerial ownership, the number of the board size, nomination and remuneration of the committee have significant impact in reducing the agency costs in the context of New Zealand-listed firms. Overall, it can be concluded that corporate governance mechanisms and ownership structures are vital in mitigating agency costs in the New Zealand context.<strong></strong></p><br />